The PMX 80 Eco is part of a series of sport headphones from Sennheiser that is packaged in bio-degradable materials to minimize the carbon footprint of the user. This marathon and gym favorite uses a verticle transducer system on a neckband that floats to keep the headphones in place during a strenuous workout. A single sided cable can eliminate cable tangles while the supplied clothing clip keeps the cable secure. The PMX 80 is sweat-proof and rinsable under running water for the ultimate in usability and durability. The rear side of the neckband is coated with a reflective stripe only visible in low-light conditions for your safety. How do they sound? You may just forget that you own home audio speakers. The Basswind system delivers clean, clear bass and the verticle transducer system channels high quality audio to the ear for an optimum listening experience. They are cold-weather tested for use indoors or out. Built-tough with a 2 year warranty.